Hierarchical storage technology heightens the utilization efficiency of a storage apparatus. In hierarchical storage technology, a hierarchical pool is formed using multiple types of storage devices having respectively different performances. A real storage area (also called a real area), which is amassed in this hierarchical pool, is allocated to a virtual logical volume.
In hierarchical storage technology, a storage destination for virtual logical volume data is changed either automatically or manually to a tier with appropriate performance based on the I/O (Input/Output) load with respect to this data. Frequently accessed data is stored in a high-performance tier, and infrequently accessed data is stored in a low-performance tier. The use of hierarchical storage technology makes it possible to allocate to the data only the needed portion of a storage device (s) having the performance required for this data.
Patent Literature 1 discloses hierarchical storage technology, which enables the I/O load to be measured for each piece of data included in a virtual storage area called a page, and to change the data storage destination in units of one page (Patent Literature 1).
Patent Literature 2 discloses technology for utilizing a priority, utilization rate, or performance requirement information of an application program to dynamically reallocate a page (Patent Literature 2).